Ligation of CD24 expressed by oral epithelial cells induces kinase dependent decrease in paracellular permeability...

Area of Science:

• Oral biology
• Immunology
• Epithelial biology

Background:

• CD24 is highly expressed in oral epithelium, particularly at sites of periodontal disease.
• Serum antibodies against CD24 correlate with reduced periodontal disease severity.
• Epithelial barrier dysfunction is a hallmark of periodontal lesions.

Purpose of the Study:

• To investigate the role of CD24 ligation in regulating epithelial tight junction formation and barrier function.
• To elucidate the specific tight junction proteins and signaling pathways involved in CD24-mediated barrier enhancement.
• To correlate in vitro findings with observations in healthy and diseased periodontal tissues.

Main Methods:

• Utilized an oral epithelial cell culture model mimicking periodontal epithelia.
• Applied anti-CD24 antibodies to induce CD24 ligation and assessed tight junction formation.
• Quantified mRNA and protein expression of tight junction components (occludin, claudins, JAM-A, ZO-1/2) using qPCR and Western blotting.
• Performed live-cell imaging to evaluate paracellular diffusion.
• Investigated the role of c-Src kinase using kinase inhibitors and assessed its phosphorylation.
• Tested the effect of blocking antibodies against JAM-A and claudins on CD24-mediated barrier enhancement.

Main Results:

• CD24 ligation by anti-CD24 antibodies induced tight junction formation and reduced paracellular diffusion.
• Significant upregulation of mRNA and protein for zona occludens-1/2, JAM-A, occludin, and claudins-4, -15 at cell contacts was observed.
• c-Src kinase activation was identified as a key mediator of diffusion-limiting tight junction complex development.
• Blocking antibodies against JAM-A and claudin-15, and partially claudin-4, abrogated the barrier-enhancing effects of anti-CD24.

Conclusions:

• Antibodies to CD24 promote the expression and localization of JAM-A and specific claudins (4, 15), enhancing epithelial barrier function.
• This CD24-mediated enhancement of the epithelial barrier plays a protective role against bacterial products in periodontal disease.
• The c-Src kinase pathway is critical for establishing these protective, diffusion-limiting tight junction complexes.